1. From the MRC Centre of Epidemiology for Child Health, Institute of Child Health, and2Institute of Ophthalmology, University College London, London, United Kingdom;
2. From the MRC Centre of Epidemiology for Child Health, Institute of Child Health, and
3. Institute of Ophthalmology, University College London, London, United Kingdom;
4. Twin Research and Genetic Epidemiology Unit, Kings College London, London, United Kingdom; and
5. Genome Research Center, The University of Hong Kong, Hong Kong, SAR, China.